[RetSignman]

Here's a test you can do at home to debunk the theory, that when glaciers melt the sea levels rise.

Fill a glass full of ice cubes, then add as much water to it as you can and wait for it to melt. The glass will NOT overflow. It's all about displacement and gases in ice.

[snakeoil]

How much of the Glaciers is above water and not at water level. So much for your displacement theory.
We are skating on thin ice- Reason, your guess is as good as mine. It appently has happened millions of years ago and will probably happen again.